The present invention relates to automatic molded case industrial circuit breakers and particularly to such circuit breakers having static or solid state trip units instead of the traditional thermal-magnetic trip units.
Electronic solid state trip units are increasingly being implemented in industrial circuit breakers in place of the traditional thermal and magnetic trip units to initiate circuit interruption automatically in response to an abnormal current condition in a protected load circuit. The increasing popularity of static trip units is largely due to their inherent versatility and rather precise repeatability of selected trip-time response characteristics. That is, a circuit breaker static trip unit can be designed to accommodate a wide range of user selected response characteristics calculated to establish a highly repeatable trip-time curve rather precisely tailored to a particular load so as to afford a full measure of overcurrent protection ranging from light overload to heavy short circuit proportions. Another attractive aspect of static trip units is that they can be readily and economically supplemented to also afford ground fault protection for a load circuit. In fact, the extreme versatility of modern static trip units presents a potential customer for an industrial circuit breaker with numerous options, i.e., functions, analogous to what one faces when buying a new automobile.
In applicants' commonly assigned, copending application entitled "Static Trip Unit for Molded Case Circuit Breakers" Ser. No. 130,321, filed concurrently herewith, there is disclosed and claimed a static unit assembled from interchangeable current transformer and electronic programmer modules. This modularization of the major trip unit components accommodates trip unit assembly and installation into a circuit breaker at the distributor level, thus significantly expediting customer service. Moreover, circuit breakers in the field can be readily converted and serviced by interchanging one or both of these modules. Obviously, it is critically important that both trip unit modules be present, properly assembled and correctly installed, if the circuit breaker is to perform its assigned circuit protective functions. Equally critical is the necessity that the trip solenoid be properly installed to act in tripping its circuit breaker in response to trip signals issued by the trip unit.
It is accordingly an object of the present invention to provide a trip interlock for utilization in a static trip industrial circuit breaker.
A further object is to provide a molded case industrial circuit breaker including a removable static trip unit and having a trip interlock operable to abort resetting of the circuit breaker in the event the static trip unit is not properly installed.
Yet another object is to provide a static trip circuit breaker of the above character, wherein the trip interlock further operates to abort circuit breaker resetting in the event the requisite trip solenoid is not installed in the circuit breaker.
An additional object is to provide a static trip circuit breaker of the above character wherein the trip interlock also operates to defeat circuit breaker resetting if the trip solenoid is not properly electrically connected with the static trip unit.
Still another object is to provide a trip interlock of the above character which is efficient in construction and reliable in operation.
Other objects of the invention will in part be obvious and in part appear hereinafter.